3 pc sql database question??????

I have purchased some software that uses the sql server backbone and am in need of some help?. I run a small business with currently 3 pcs that use a excel spreadsheet to quote customers. I have purchased a product named in flow inventory and would like to start using it in my business. I have tried using a pc with a 2gig processor and 2 gb of memory as a server but it is running very slow. I need to be able to quote to customers straight away so I have uploaded 200000 items from various suppliers into it and even on my laptop as a stand alone database it runs slow and that only has 512mb of memory so i would expect that. I am thinking of buying a 6gb laptop with a 2.5gb proccesor and I want to build a pc with a 3.0gb proccesor and 8gb of memory to act as a server with a sata drive and so on as I cannot afford a server. I currently have 3 pcs running through a adsl router to network them and I understand I need to use a switch between these computers to make them throughput data quicker. I just need some help would this pc act as a server ok for this amount of data as I cannot afford a server.

What are the minimal requirements for the product you bought?
Bear in mind that those are the MINIMAL requirements so the program will run, just about, so if you want some decent performance then you'll have to increase the specification - but by how much depends on what is specified and on what basis that specification was made.
Perhaps if you contact the people who wrote the application and ask them what kind of hardware you need if you're going to use their software with a 200,000 item repository, and want to be able to quote in (insert maximum time here).

You don't need a server as such; often this just means a file server with a huge hard drive. 1TB drives are very cheap these days - I just got one yesterday - so you don't need a server for that. But the server issue is a different question.

Note that not everything is measured in GB (gigabytes). Hard disk and RAM are specified in GB; a CPU is specified in a number of terms of which MHz/GHz (mega/gigahertz) is one, and not a very good one at that, because it's easy enough for processor manufacturers to ramp up the GHz without any real increase in processor performance - a 4GHz processor that has an average instruction time of 4 clock cycles will perform just as well as a 2GHz processor that has an average instruction time of 2 clock cycles.

Any network hub is likely to improve your data transfer rate between the computers. Ethernet hubs that can handle 10Mb/s are very easy to come by, I have at least two, one of which I'm using right now, and that is plugged into my modem (which itself has hub functionality, but I don't use that between my main computers).

sorry what exactly do you want to know?
If the current hardware does the job then I'd say leave it. Are you sure it's the router that's the bottleneck? The ADSL part of it will run at ADSL speed, i.e. a few Mbit/s, but the rest of the switch circuit should operate at full speed. Do you know which one you've got? (It'll probably be marked somewhere on the unit)
Also it might be worth letting us know where on the planet you are; this could make a difference to what's available.